Spark tester

ABSTRACT

A spark tester having a base plate of insulating material. A central post carries a sharp edged disc electrode. Clamps surround the post and carry needle-pointed radially extending electrodes. Fasteners for the post and clamps extend into upright sockets in the base plate. Transverse bores intersect the upright sockets. Fasteners for the clamps engage cable conductors in associated transverse bores with cable insulation extending into the transverse bores. A ground wire extends into the transverse bore associated with the post to ground the disc electrode.

[4 Aug. 6, 1974 United States Patent [191 Maynard PrimaryExaminer-Michael J. Lynch Agent, or Firm-James W. Pearce; Roy F.

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UNITED STATES PATENTS ductors in associated transverse bores with cableinsu- 324/l8 lation extending into the transverse bores. A ground 324/18wire extends into the transverse bore associated with 324/18 the post.to ground the disc electrode. 324/18- 6 Claims, 5 Drawing Figures1,316,560 9/1919 1,526,897 2/1925 Boselli 1,605 863 11/1926 Stem2,005,992 6/1935 Heaton PATENIEDAUE 61914 3.828.24

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SHEET 2 OF 2 SPARK TESTER This invention relates to spark testersemployed in determining the quality of the spark delivered by a highvoltage ignition system such as that used on late model outboard enginesor other reciprocating engine and ignition system combinations.

An object of this invention is to provide a spark tester capable oftesting the electrical discharge power to all cylinders of areciprocating engine simultaneously.

Another object of this invention is to provide such a spark tester inwhich there are insulated current paths, insulated joints, and insulatedconnectors that shield the high voltage of the ignition system fromarcing or discharging at random places along the spark tester.

Briefly, this invention provides a spark tester having a plate-likeinsulative base at the center of which is mounted a post which carries adisc-shaped sharp edged electrode. The post is hollow and is held inplace by a fastener which extends into the base and into an elongatedbore which extends from one side of the base parallel to and spacedbetween faces thereof. An insulated ground lead extends into theelongated bore and is provided with an enlarged head which is engaged bythe fastener to connect the ground lead to the discshaped sharp edgedelectrode. A plurality of spaced electrode holders are mounted on thebase surrounding the disc-shaped electrode. Each of the electrodeholders carries a needle type electrode extending radially of thedisc-shaped electrode with the point of each needle electrode spaced anadjustable distance from the sharp edge of the disc electrode. Each ofthe electrode holders is supported by a fastener which extends into thebase and into a bore which extends from a side of the base parallel toand spaced between the faces of the base. Test cables extend into thelast mentioned bores and are connected to the electrode holders by thefasteners associated therewith. Opposite ends of the test cables areattached to spark plug cables of a motor to be tested.

The above and other objects and features of the invention will beapparent to those skilled in the art to which this invention pertainsfrom the following detailed description and the drawings in which:

FIG. 1 is a plan view of a spark tester constructed'in accordance withan embodiment of this invention in association with a fragmentaryportion of an internal combustion engine of marine type; I

FIG. 2 is a sectional view taken on the line 2-2 in FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is a sectional view taken on the line 4-4 in FIG. 1; and

FIG. 5 is a view partly in side elevation and partly in section of theconnection between a spark plug lead cable and a test cable.

In the following detailed description and the drawings, like referencecharacters indicate like parts.

FIG. 1 shows a spark tester which is constructed in accordance with anembodiment of this invention. The tester 10 includes a plasticinsulating plate-like base 11 containing an upright threaded hole orsocket 12 (FIG. 2) which intersects an elongated hole or bore 13. Thehole 13 is parallel to and spaced between an upper face 131 and to alower face 132 of the base 11 and extends inwardly from a side face 133of the base 11. An end portion of a ground cable 14 extends into theelongated hole 13. External insulation'141 of the ground cable 14 is ofapproximately the same diameter as the hole 13 and extends into the hole13 to adjacent the upright hole 12. A conductor 142 of the cable 14extends inwardly of the inner end of the insulation 141. A soft metalplug 15 of solder metal or the like is mounted on the inner end'portionof the conductor 142. The plug 15 isengaged by an upright screw 16 thatis threaded into hole 12 to provide a good electrical contact betweenthe screw 16 and the conductor 142. The hole or bore 13 is large enoughin diameter to accept the plug 15 and the cable 14 with its insulationintact. This method of attachment provides a well insulated junctionbetween the screw 16 and the conductor 142 of the cable 14. The otherend of the conductor 142 of the cable 14 is fitted with an alligatorclamp 40 (FIG. 1) for attachment to some appropriate zero potentialreference, such as an engine block 17 of an engine 171, as shown inFIG. 1. The screw 16 (FIG. 2) holds in place a tubular spacer or thimble18, which forms a post on which a sharp edged annular electrode disc 19is mounted. The disc 19 is disposed parallel to and spaced from theupper face 131 of the base 11.

In FIGS. 1-3 are shown needle-point electrode rods 20. The electroderods are held adjustably and slidably by electrically conducting springclamps 21. The electrode rods are disposed around the disc 19 in aradial orientation to form adjustable spark gaps 22 between the rods 20and the sharp edge disc 19.

The spring clamps 21, which hold the electrodes 20, are held in place onthe base 11 by screws 23,'as shown in FIG. 3. The screws 23 are threadedinto upright holes or sockets 24. Each of the holes 24 communicates withone of a plurality of holesor bores 25 in the base 11 which receive endportions of spark plug connector test cables 26. Details of constructionof one of the holes 25 and associated members are shown in FIG. 4. Thehole 25 extends inwardly from a side face 261 of the base 11 and isintersected by the hole 24. A soft metal plug 27of solder metal ismounted on an inner end portion of a conductor 262 of the cable 26.Insulation 28 of the cable 26 continues uninterrupted up to the plug 27.The insulation 28 continues into the associated hole 25 to form a wellinsulated connection for the cable 26 and the screw 23. As shown, thediameters of the insulation 28 and of the plug 27 are substantiallyequal to the diameter of the hole 25. The screw fastener 23 engages andfirmly grips the plug 27 to provide a good electrical connection betweenthe conductor 262 and the clamp 21 and through the clamp 21 to theassociated electrode rod 20 (FIGS. 1 and 3). Referring to FIG. 1, thefree end of each of the test cables 26 plugs into one of a plurality ofspark plug caps 29 that have been removed from their respective sparkplugs 291. FIG. 5 shows the internal arrangement of one of the sparkplug caps 29 and associated members. The spark plug cap 29 includes aspring coil 30 and an arm 31 that pierces insulation 32 of a spark plugcable 33 to provide an insulated current path between a cable wire 34and the coil 30. An insulator cap 35 is formed around the coil 30 andthe cable 33. The free end of the conductor 262 of the cable 26 isfitted with a soft metal plug 36 of solder metal or the like, of adiameter to be received and resiliently gripped by the spring coil 30.Insulation 28 of the cable 26 continues uninterrupted up to said plug36. The intersection of the plug 36 and the insulation 28 is covered andinsulated by a sleeve 37 of insulating material which is resilientlyelastic such as rubber or other rubber-like material. When the plug 36is snugly pushed into the coil 30, the sleeve 37 continues into the plugcover 35 to form a well insulated current path.

The spark plugs 291 can be left in the engine block 17 so that a test ofall cylinders can be made simultaneously as a starter (not shown) turnsthe engine 171 to provide starting RPM and cylinder pressure. Thespacing between the needle-points of the electrode rods and the sharpedge of the electrode disc 19 can be set at the distance to define aspark of the strength required for proper operation of the engine 171,and as the engine is turned on, the spark available at all spark plugscan be viewed during a single test.

The spark tester constructionillustrated in the drawings and describedabove is subject to structural modification without departing from thespirit and scope of the appended claims.

Having described my invention, what I claim as new and desire to secureby letters patent is:

1. A spark tester for an engine which comprises a base plate ofinsulating material, a post mounted on one face of the base plate spacedfrom sides thereof, a sharp edged disc electrode mounted on the post, aplurality of clamps mounted on said face spaced from the post, afastener of conductive material holding the disc electrode and the poston the base plate and extending into an upright central socket in thebase plate, a fastener of conductive material holding each of the clampson the base plate and extending into an upright outer socket in the baseplate, a transverse bore intersecting each of the upright sockets, thetransverse bores beng spaced, each of the transverse bores extendingfrom a side of the base plate and being spaced between upper and lowerfaces of the base plate, a cable having a central conductor and externalinsulation extending into each of the transverse bores associated withone of the clamps, the insulation terminating inside the associatedtransverse bore, means on the cen-v tral conductor engaged by theassociated fastener to provide an electrical connection between eachclamp and the associated central conductor, a ground wire extending intothe transverse bore associated with the post, means on the ground wireengaged by the post fastener for connecting a free end of the groundwire to the engine, means for connecting free ends of the conductors ofthe other cables to spark plug connectors of the engine, and aneedle-pointed electrode mounted on each of the clamps, theneedle-pointed electrodes extending radially of the disc electrode,pointed ends of the needle-pointed electrodes being spaced from the discelectrode to define spark gaps for testing the spark of the engine.

2. A spark tester as in claim 1 wherein the means on the conductorengaged by the associated fastener is a plug of metal on the conductorinside the associated transverse bore of substantially the same diameteras the associated transverse bore, the plug being engaged by theassociated fastener.

3. A spark tester which comprises an insulative base, a conductiveground screw mounted centrally thereon, said screw holding in verticalspaced relation thereto a disc-shaped sharp edge electrode, saidelectrode electrically communicating through the conductive ground screwwith a soft metal plug forming a terminus of a ground cable and securelyheld by the conductive screw in a socket inside the insulative base,means for connecting an opposite terminus of the ground cable to anengine, a plurality of needle-point electrode rods arranged around andextending radially of the discshaped sharp edge electrode, a pluralityof spaced spring clamps mounted on the base surrounding and spaced fromthe conductive ground screw, each of the spring clamps supporting one ofthe electrode rods, each of said clamps being fastened to the insulativebase by a conductive test cable screw whcih communicates with a softmetal plug formed on an end of a spark plug test connector cable andsecurely held by the conductive test cable screw in a cable bore insidethe insulative base, and means for connecting opposite ends of the testconnector cables to spark plug cables of the engine providing a multiplegap spark tester for testing the voltage applied to a plurality of thespark plug cables simultaneously.

4. A spark tester as in claim 3 in which the ground cable is slidablyinstalled through a bore in the insulative base, .the ground cablecarries insulation in adjacent relationship to the soft metal plug atthe first mentioned end thereof, and the metal plug and the cableinsulation extend deeply into the bore for full insulation of theconnection between the soft metal plug and the conductor ground screwinside the insulative base.

5. A spark tester as in claim 3 wherein each of the connector cables isslidably installed through a bore in the insulative base, each connectorcable is provided with insulation in adjacent relationship to the softmetal plug at an end thereof, the metal plug and the cable insulationextending deeply into the associated bore for full insulation of theconnection between the soft metal plug and the conductive test cablescrew associated therewith inside the insulative base.

6. A spark tester as in claim 3 wherein the means for connectingopposite ends of the test connector cables to the spark plug cablesincludes a soft metal plug on the opposite end of each connector cable,the cable insulation terminating adjacent thereto; an insulating sleevecovering portions of the insulation of the cable and of the associatedplug, the insulating sleeve extending into the spark plug cap to providean insulated junction between the spark plug cap and the associatedspark plug connector cable.

1. A spark tester for an engine which comprises a base plate ofinsulating material, a post mounted on one face of the base plate spacedfrom sides thereof, a sharp edged disc electrode mounted on the post, aplurality of clamps mounted on said face spaced from the post, afastener of conductive material holding the disc electrode and the poston the base plate and extending into an upright central socket in thebase plate, a fastener of conductive material holding each of the clampson the base plate and extending into an upright outer socket in the baseplate, a transverse bore intersecting each of the upright sockets, thetransverse bores beng spaced, each of the transverse bores extendingfrom a side of the base plate and being spaced between upper and lowerfaces of the base plate, a cable having a central conductor and externalinsulation extending into each of the transverse bores associated withone of the clamps, the insulation terminating inside the associatedtransverse bore, means on the central conductor engaged by theassociated fastener to provide an electrical connection between eachclamp and the associated central conductor, a ground wire extending intothe transverse bore associated with the post, means on the ground wireengaged by the post fastener for connecting a free end of the groundwire to the engine, means for connecting free ends of the conductors ofthe other cables to spark plug connectors of the engine, and aneedle-pointed electrode mounted on each of the clamps, theneedle-pointed electrodes extending radially of the disc electrode,pointed ends of the needle-pointed electrodes being spaced from the discelectrode to define spark gaps for testing the spark of the engine.
 2. Aspark tester as in claim 1 wherein the means on the conductor engaged bythe associated fastener is a plug of metal on the conductor inside theassociated transverse bore of substantially the same diameter as theassociated transverse bore, the plug being engaged by the associatedfastener.
 3. A spark tester which comprises an insulative base, aconductive ground screw mounted centrally thereon, said screw holding invertical spaced relation thereto a disc-shaped sharp edge electrode,said electrode electrically communicating through the conductive groundscrew with a soft metal plug forming a terminus of a ground cable andsecurely held by the conductive screw in a socket inside the insulativebase, means for connecting an opposite terminus of the ground cable toan engine, a plurality of needle-point electrode rods arranged aroundand extending radially of the disc-shaped sharp edge electrode, aplurality of spaced spring clamps mounted on the base surrounding andspaced from the conductive ground screw, each of the spring clampssupporting one of the electrode rods, each of said clamps being fastenedto the insulative base by a conductive test cable screw whcihcommunicates with a soft metal pLug formed on an end of a spark plugtest connector cable and securely held by the conductive test cablescrew in a cable bore inside the insulative base, and means forconnecting opposite ends of the test connector cables to spark plugcables of the engine providing a multiple gap spark tester for testingthe voltage applied to a plurality of the spark plug cablessimultaneously.
 4. A spark tester as in claim 3 in which the groundcable is slidably installed through a bore in the insulative base, theground cable carries insulation in adjacent relationship to the softmetal plug at the first mentioned end thereof, and the metal plug andthe cable insulation extend deeply into the bore for full insulation ofthe connection between the soft metal plug and the conductor groundscrew inside the insulative base.
 5. A spark tester as in claim 3wherein each of the connector cables is slidably installed through abore in the insulative base, each connector cable is provided withinsulation in adjacent relationship to the soft metal plug at an endthereof, the metal plug and the cable insulation extending deeply intothe associated bore for full insulation of the connection between thesoft metal plug and the conductive test cable screw associated therewithinside the insulative base.
 6. A spark tester as in claim 3 wherein themeans for connecting opposite ends of the test connector cables to thespark plug cables includes a soft metal plug on the opposite end of eachconnector cable, the cable insulation terminating adjacent thereto, aninsulating sleeve covering portions of the insulation of the cable andof the associated plug, the insulating sleeve extending into the sparkplug cap to provide an insulated junction between the spark plug cap andthe associated spark plug connector cable.